1. Field of the Invention
The present invention relates to a semiconductor circuit, and more particularly, to a transconductor capable of substantially canceling or reducing an output direct current (DC) offset caused by an input DC offset or mismatch between input terminals of the transconductor, and a method thereof.
2. Description of the Related Art
Generally, a DC offset occurring between signals input to a mixer included in a direct conversion transmitter (DCT) greatly affects characteristics such as carrier leakage suppression and image rejection. In particular, since carrier leakage is very sensitive to the DC offset, it greatly degrades adjacent channel power rejection (ACPR) and a maximum output power dynamic range. Accordingly, when the DC offset is substantially canceled, the carrier leakage is reduced.
However, when a capacitor with large capacitance is provided or digital circuit blocks such as an analog-to-digital converter and a digital-to-analog converter are implemented in the DCT to reduce the DC offset, the capacitor and the digital circuit blocks cover a large area and have a large current consumption. Accordingly, use of such capacitors or digital blocks is not appropriate to a trend toward compactness and low power consumption in the communications market.